Impaired heart rate variability as a marker of cardiovascular autonomic dysfunction in multiple sclerosis

Abstract

Multiple sclerosis (MS) can cause alterations in autonomic cardiovascular functions. We aimed to investigate the correlation of disease activity and disability with heart rate variability (HRV) of cardiovascular autonomic dysfunction (CAD) demonstrated by 24-h Holter monitorization. Thirty-four patients with clinically active relapsing-remitting MS, age 33.8 ± 7.6 years, were studied. Twenty healthy volunteers served as controls. The time domain long-term HRV parameters were recorded by a digicorder recorder calculated by ambulatory electrocardiograms.Variabilities in time domain were lower in the MS patients: SDNN (standard deviation of all R-R intervals, p = 0,019), SDANN (standard deviation of the averages of R-R intervals in all 5-minute segments of the entire recordings, p = 0,040), RMSSD (the square root of the mean of the sum of the squares of differences between adjacent R-R intervals, p = 0,026), HRVM (mean of the SDNN in all the 5-minute intervals, p = 0,029), HRVSD (standard deviation of the SDNN in all the 5-minute, p = 0,043). These results suggest that MS causes CAD manifesting as long-term HRV abnormalities. This illness seems to cause a dysfunction in parasympathetic cardiovascular tone. Depressed HRV parameters are independent from the clinical findings, but the illness progression partially seems to provoke a decrease in such parameters.